[Due for payment 2026-03-24] Migrate the main chat list to FlashList

[roryabraham]

HOLD on:

• Comment linking to be 100% complete
• The new architecture to be enabled (this is not a hard requirement but I have a hunch that this should wait on that too)

Problem

The main chat list is one of the most, if not the most important component in our app. If you scroll far or fast on this list, you may see frames drop. Furthermore, there are some known performance issues with this list (example). We have already migrated almost every other virtualized list in our app from FlatList to FlashList, because its performance is much better.

Solution

Let's build support for bidirectional pagination in FlashList, then enable it on the main chat list in E/App.

Issue Owner

Current Issue Owner: @situchan

[melvin-bot]

Triggered auto assignment to @garrettmknight (NewFeature), see https://stackoverflowteams.com/c/expensify/questions/14418#:~:text=BugZero%20process%20steps%20for%20feature%20requests for more details.

[roryabraham]

I expect this to be on HOLD until sometime in February, if not later, so I'm moving this back to monthly

[roryabraham]

cc @muttmuure adding this to the New Expensify performance improvements project. I acknowledge that the problem statement is a bit of a reverse-solution but I think it's a good bet that this will provide substantial performance improvements, as FlashList is just much better for performance than FlatList. We've established that elsewhere where we've migrated to FlashList